Uhm john I want to make his led project and since already did and I'm alil confused I thought I'd ask you uhm how does the music play if you use the headphone Jack because I want to use it with my stereo system and Idk how

This circuit should, like any circuit ,have current limiting. A simple resistor in series with the leds could limit the current, protecting the leds and the transistor. The transistor is being used in switching mode ( no bias voltage divider on the base) and will turn on only when the base is more than .6v positive relative to the emitter. When it turns on, the current is only limited by the voltage drops of the emitter to collector voltage added to the voltages dropped across the leds, which are about 1.65 volts each. I would not build it with no current limiting resistor. The resistor should limit the current to less than the max current rating of the lesser of the current max of the transistor or a led. I would limit current to about .02 amps.